Machining

Precise material removal to bring a part to specified size

• Automotive machining examples Boring cylinders Honing cylinders Grinding cranks and cams Grinding or milling heads and blocks Grinding flywheels

Copyright 2003 Gary Lewis – Dave Capitolo

Drilling and reaming for valve guides

Machining

Drilling

• End cutting• Used for roughing holes to size• Reamers finish holes to size and

surface finish

Machining

Turning & boring

• Turning – outside diameter with single pointed tools on a lathe

• Boring – inside diameter with single pointed tools on a lathe

Machining

Milling

• Vertical spindle• Used to remove material from a flat surface

Machining

Milling

• Typical milling cutters HSS & carbide

Machining

Grinding

• Abrasive machining using millions abrasive grains• Minimal stock removal• High surface finish quality

Vertical spindle surfacing

• Used to grind flywheels, blocks, and cylinder heads

Machining

Horizontal spindle grinders

• Used for valve grinders, crankshaft grinders, and camshaft grinders

Machining

Broaching

• Chip removal is done with progressively larger cutting teeth

• Keyways in sprockets and gears• Not done in auto machine shops

Machining

Tool materials

HSS (High speed steel)• Drills, reamers, and milling cutters• Tungsten, vanadium, and cobalt added for hardness

Tungsten carbide• Boring bars and cutter of a face mill• Attached to a tool holder • Heat resistant and operate at high speeds

(up to 3 times HSS)

• Cobalt increased for shock resistance

Machining

Tool materials

Tungsten Carbide (cont.)• As cobalt % increases, resistance to shock increases, &

resistance to heat decreases

Aluminum Oxide grinding wheel• Used for steel & nodular iron (cranks & cams)

Silicon Carbide grinding wheel• Used for iron (heads & blocks)

Machining

Lathe tool

Machining

• Rake angles form the surface that the chips pass over• Back rake angle angles are greater for boring

Machining

• Relief angles prevent the cutting tool from bumping into the work

Machining

• Nose radius affects surface finish• Large radius increases power required and tool chatter

Machining

Side cutting angle• The greater the angle, the more tool deflection

• The smaller the angle, the bigger the chip and more the tool will wear

Machining

Cutting oils• Extend tool life• Cool cutting tool• Cast iron can be machined without cutting oil• Aluminum requires cutting oil• All threading operations require cutting oil

Machining

End mills• Used to remove chips from the end or the side of tool

• ‘Two flute’ cutters cut from the end

• Cutters with more than two flutes are used for cutting on the side

Machining

Spindle tilt• The spindles of automotive surfacing machines are tilted about .004”

• This produces a ‘hollow cut’ of less than .0005”

Machining

Conventional vs. climb milling

• Conventional – Cutter rotates opposite direction of feed

• Climb – Cutter rotates same direction as feed

Machining

Drill bits• Available in fraction, letter, or number sizes• End cutting• Helical flutes for chip removal• Length & angle of cutting edges should be equal

Machining

Drill bits (cont.)• Morse taper (5/8” per foot), drift needed for removal

• Center drill (60°), for pilots and machining centers

Machining

Core drills and countersinks

• Core drills enlarge holes only, will not cut in center

• Countersinks chamfer bolt holes (82°)

MachiningHand reamers• Cut material for a distance on the end (1/16” per foot)

• Cut material on a short 45° angleMachine reamers

• Cut only .003” to .005”

• Cut only 5% material

Machining

Counter bores• Spot-facing head bolt holes

Machining

Grinding• Diamond dresser (trues wheels)• Star wheel dresser (does not true wheel)

Machining

Hard grinding action• No wheel breakdown• Little material removal• Burnt work• Wheel needs dressing

Soft grinding action

• Too much wheel breakdown• Stone material gets caught between wheel and work• Rough surface finish

Machining

Honing• Slower speed than grinding• Honing stones must also break down• Honing oils cool the work and flush away the grit